linux-kernel - Re: [PATCH v6 2/2] kasan: Add memzero int for unaligned size at DEBUG

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Message-ID: <CA+fCnZfKAZuy9oyDpTgNUTcNz5gnfHpJK5WN-yBNDV5VF8cq0g@mail.gmail.com>
Date:   Mon, 5 Jul 2021 13:23:17 +0200
From:   Andrey Konovalov <andreyknvl@...il.com>
To:     Marco Elver <elver@...gle.com>
Cc:     yee.lee@...iatek.com, LKML <linux-kernel@...r.kernel.org>,
        nicholas.tang@...iatek.com,
        Kuan-Ying Lee <Kuan-Ying.Lee@...iatek.com>,
        chinwen.chang@...iatek.com,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "open list:KASAN" <kasan-dev@...glegroups.com>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v6 2/2] kasan: Add memzero int for unaligned size at DEBUG

On Mon, Jul 5, 2021 at 1:18 PM Marco Elver <elver@...gle.com> wrote:
>
> On Mon, 5 Jul 2021 at 13:12, Andrey Konovalov <andreyknvl@...il.com> wrote:
> [...]
> > > +       /*
> > > +        * Explicitly initialize the memory with the precise object size to
> > > +        * avoid overwriting the SLAB redzone. This disables initialization in
> > > +        * the arch code and may thus lead to performance penalty. The penalty
> > > +        * is accepted since SLAB redzones aren't enabled in production builds.
> > > +        */
> > > +       if (__slub_debug_enabled() &&
> >
> > What happened to slub_debug_enabled_unlikely()? Was it renamed? Why? I
> > didn't receive patch #1 of v6 (nor of v5).
>
> Somebody had the same idea with the helper:
> https://lkml.kernel.org/r/YOKsC75kJfCZwySD@elver.google.com
> and Matthew didn't like the _unlikely() prefix.
>
> Which meant we should just move the existing helper introduced in the
> merge window.
>
> Patch 1/2: https://lkml.kernel.org/r/20210705103229.8505-2-yee.lee@mediatek.com

Got it. Thank you, Marco!